Currently, in oil extracting fields, beam pumping units are gradually being replaced by tower-type oil pumping units resulting from their benefits of a simpler structure, simpler operation and maintenance, low unit cost, and low energy consumption. A Chinese application for a utility patent—Application No. 2008102388641.1—has been published in China on a combination drive tower pumping unit. The drive system of the unit employs belts, chains, or combinations of belts and chains in combination with a permanent magnet synchronized braking motor of low-speed and large-torque. The drive system transfers mechanical power to a first transfer shaft in a first stage speed reduction and to a second transfer shaft in a second stage speed reduction via a pair of gears. This transfer causes the drive wire rope and balance weight pull rope, both of which are wrap fastened to the wire rope wheel, to move sucker rods and a balance weight box in an up and down motion to accomplish oil pumping tasks. Using a chain or a belt and chain combination to achieve the first stage speed reduction has the benefits of reducing mechanical power loss, maintaining higher operating efficiency under large load, and reducing noise level in environment sensitive area. The drawback of such tower pumping units is added effort and low work efficiency during oil well workover, such workover requiring that the wire rope wheel, weighing several tons as a large diameter wheel, be moved away from its working position.
Accordingly, there is a need for a tower pumping unit that provides a moving system to allow for well workover in an easier and more efficient manner. The present invention fulfills these needs and provides other related advantages.